Hydraulic turbine



July 20, 1954 P. w. SEEWER HYDRAULIC TURBINE Filed March 27. 1951Patented July 20, 1954 HYDRAULIC TURBINE Paul Werner Seewer, Rugby,England yassignor to :The English Electric Company Limited, London,England, a British company Application March 27, 1951, Serial No.217,778

Claims priority, application Great Britain April 14, 1950 3 Claims.

The invention relates to hydraulic turbines of the impulse Wheel type,and has the object of limiting the runaway speed of such turbines.

According to the main feature of the invention the portions of the waterjet which traverse the runner unused at overspeeds thereof are deflectedtowards the backs of the runner buckets by means of a duct having itsentrance in the line of the jet and its exit directed against the backof the buckets, i. e. in the direction opposite to their rotation, whichduct is closed or sealed during ordinary operation of the turbine at itsentry by a bursting diaphragm which is so dimensioned as to withstandthe action of spray water but to be burst open by the impact of theportions of the jet passing through the buckets of the runner unused ata predetermined overspeed. Thereby spray water is prevented from beingdirected unintentionally against the backs of the buckets and fromproducing an adverse effect on the efiiciency of the turbine in normaloperation, while a powerful braking action is exerted on the latter uponreaching a predetermined overspeed condition.

In order that the invention may be better understood and readily carriedinto effect an embodiment thereof will now be described by way ofexample with reference to the accompanying drawing which is adiagrammatic side elevation of the relevant part of an impulse wheeltype hydraulic turbine.

In the casing I the runner 2 is journalled on its shaft 3 and carriesbuckets 4. A jet of water is directed tangentially on to the buckets 4from a nozzle 5 attached to the casing I which nozzle is controlled by aneedle valve 6. A curved duct 1 is arranged in the casing l opposite thenozzle 5 the entrance of which duct lies in the projected path of thewater jet, and the exit of which is directed against the back of thebuckets 4.

The entrance of the duct 1 is sealed by a bursting diaphragm 8 which isso dimensioned as to withstand the action of the spray of water hittingit incidentally, but to be burst open by the portions of the jet passingunused through the buckets at a predetermined overspeed.

These portions of the water are then directed by the duct 1 against theback of the rotating buckets 4 and exert a powerful braking action onthe runner 2 which prevents it from attaining an excessive and dangerousoverspeed. For example, the runaway speed of an impulse type turbinewhich has been hitherto of the order of 80% above the normal speed, cannow be re- 2 duced to or even 50% of the latter, whereby the stresses inthe runner, the buckets and the fixtures are reduced to 80% and evenThereby it is made possible to build impulse wheel type turbines of highoutput (say 140,000 kw.) for an ordinary operational speed of 300 R. P.M. instead of 200 R. P. M. whereby considerable savings in first costsboth of the turbine and of an electric alternator driven by it can bemade.

Impulse wheel type turbines having more than one jet per runner can beprovided with a deflecting duct for each jet, or alternatively suchducts are provided for one or some of these jets only, as indicated inchain dotted lines in the drawing.

The bursting diaphragm is preferably made up of a material which doesnot splinter or is much softer than the material of the runner or of thecasing, so that it cannot damage these components. Wood, artificialplastics, rubber or soft metal such as lead are considered suitablematerials.

While I have described hereinabove what may be considered a suitableembodiment of my invention, I do not wish to be limited to the exactdimensions and constructions shown, for obvious modifications will occurto a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent is:

1. A hydraulic turbine comprising in combination: a casing, an impulsewheel journalled for rotation inside the said casing, a plurality ofbuckets fixedly connected to said impulse wheel, a nozzle attached tosaid casing and directed towards the concave side of the said bucketstangentially to the said impulse wheel, a curved duct fixed to the saidcasing with its entrance in alignment with the said nozzle and with itsexit directed towards the convex backs of the said buckets, and adiaphragm sealing in normal operation the entrance to the said curvedduct and consisting of a material resisting the action of the spray ofwater hitting it incidentally but to be burst open by the portions ofthe jet of water passing through the buckets at a predeterminedoverspeed.

2. A hydraulic turbine as claimed in claim 1 wherein the said burstingdiaphragm consists of a splinter-free material softer than the materialof the said casing.

S. A hydraulic turbine comprising in combination: a casing, an impulsewheel journalled for rotation inside the said casing, a plurality ofbuckets fixedly connected to said impulse Wheel, at least two nozzlesattached to the said casing each directed towards the concave side ofthe said buckets at difierent positions tangentially to the said impulseWheel, at least one curved duct fixed to the said casing with itsentrance in alignment with one of the said nozzles and with its exitdirected towards the convex backs of the said buckets, and a diaphragmsealing in normal operation the entrance to the said curved duct andconsisting of a material resisting the action of the spray of waterhitting it incidentally but to be burst open by the portions of the jetof water passing through the buckets at a predetermined overspeed.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,307,703 Sagberg et a1 June 24, 1919 1,498,096 Herr June 17,1924 1,837,570 Moody Dec. 22, 1931 FOREIGN PATENTS Number Country Date46,083 Switzerland Apr. 8, 1909

